Just like missiles, guided munitions may be fitted with a steering section comprising guide vanes commonly known as canard wings or control surfaces. As it flies towards a target, the guided munition is steered by control and guidance electronics of the munition that provides closed loop control of the position of the control surfaces using motorized drive of the electric, pneumatic or pyrotechnic type.
In general, guided munitions are fired from a launch tube such as a rocket launcher, a gun barrel or a mortar tube. There are at least two main phases in the launch of a guided munition: a firing phase which ejects it from the launch tube, followed by an external ballistic phase after it has left the launch tube in order to head towards a target.
The control and guidance section of the guided munition comprises a system for controlling the control surfaces which need to be contained within the launch tube during the firing phase. The control surfaces are in a retracted position inside the launch tube and then deploy during the external ballistic phase, namely after the munition has left the launch tube. In general, the control surfaces of the guided munition deploy in an umbrella fashion, opening either in the direction of launch of the munition against the aerodynamic wind produced by the speed of the munition or in the opposite direction to the direction of launch of the munition.
The system controlling the control surfaces firstly ensures that they are kept in the retracted position allowing the munition to be inserted into the launch tube and secondly ensures that they deploy following tube exit.
Deployment of the control surfaces can be achieved either using a mechanism that operates automatically as soon as the munition is ejected, namely as soon as the steering section has left the launch tube without the need for a specific deployment command sent from the control surface operating electronics, or by another mechanism that deploys the control surfaces only on receipt of one or more commands transmitted by the operating electronics to the system controlling the control surfaces at a desired moment in the trajectory phase or external ballistic phase of the munition. In order to be compatible with both types of operation, the control surfaces control system has to be able to be configured so that when the munition leaves the launch tube the electronics, on a single command sent by the operating electronics, authorizes simultaneously the unlocking of the control surfaces retention system and the deployment of those control surfaces. In another configuration of the control surfaces control system, a first command sent by the guidance/control electronics to the control surfaces control system will allow the control surfaces to be unlocked, and a second command after the first will allow them to be deployed.
The control surfaces control system also needs to have a response time compatible with the most rapidly moving munitions, to be able to withstand firing environments of the gunshot type, and be able to be incorporated into low-caliber munitions and be reversible so that control surfaces opening tests can be performed.
However, the steering sections of the prior art do not have enough compactness or robustness to be used on increasingly high-performing guided munitions.